Deformation-based tire inflation device

ABSTRACT

A device for automatically maintaining desired air pressure within a vehicle tire utilizes deformation of the rotating tire where it contacts the road surface to operate an air compressor. The air compressor is formed in the wheel and connected to the tire, the compressor responsive to deformation of the tire causing compressed air to pass into the tire. The compressor is preferably of a reciprocating piston type having a cylinder adapted to receive a sliding piston, the piston preferably slidably received within a plunger in contact with the inside of the tire. A spring is preferably disposed between the plunger and the piston to limit the motion of the piston to a fixed displacement less than the deformation of the tire, such that the tire inflation system is operable for a wide range of deformations of the tire. Additionally, a centrifugal intake valve is preferably provided that seals off the inlet passageway to the air compressor and opens only when the wheel is rotating rapidly enough so that centrifugal force on potential liquid or particulate contaminants expels such contaminants. Advantageously, the tire inflation device of the present invention is entirely contained within the wheel, without the need for a rotating joint to the vehicle body or frame.

FIELD OF THE INVENTION

The present invention relates generally to fluid pressure controlapparatus, and more particularly to an automatic tire pressure inflationdevice which is entirely contained within a vehicle wheel, formaintaining a desired inflation pressure within a tire mounted on saidwheel.

BACKGROUND OF THE INVENTION

Maintaining correct inflation pressure in automobile tires is acceptedas an effective way to increase fuel economy, decrease tire wear andincrease safety. Although proper tire inflation may be maintained byregularly checking tire pressure and adjusting accordingly, suchmaintenance tends to be largely ignored because of the inconvenienceinvolved. Additionally, tire pressure varies based upon the pressurizedair temperature and recent driving conditions sustained by the tire.Varying tire inflation pressure depending upon the road surface offersother benefits such as improved traction, or an increase in tirepressure may be desirable to offset changes in the vehicle payload.

The need for, and interest in, finding a practical means of maintainingproper tire pressure is illustrated by at least 19 patents granted since1915, at least 13 of which have issued since 1979. Most of the prior artpatents involve devices that are not self-contained on a wheel, butrather rely on parts mounted on the vehicle body or frame andadditionally require some type of rotating joint, be it mechanical,electrical or pneumatic. Such rotating joints are expensive andimpractical in the adverse environment in which vehicle wheels operate,including contaminants such as oil, water, dirt and sand which tend toattack seals necessarily a part of such rotating joints.

For example, U.S. Pat. No. 5,325,902 issued to Loewe et al., and herebyincorporated by reference, describes an automatic tire pressure monitorand inflation system having an electric motor, an air compressordisposed upon the rotating wheel, and an electrical generator. Thegenerator includes coils mounted on the rotating wheel and a magnetmounted on a non-rotating portion of the vehicle. Thus, this systemincludes a rotating connection, albeit without physical contact, inwhich the wheel-mounted components of the generator will interact withthe vehicle-mounted components thereof, to induce a voltage for drivingthe electric motor.

Other contemplated apparatus contained entirely on a rotating vehiclewheel include stored compressed gas or stored energy sources on thewheel which must be periodically recharged or replaced, offering limitedadvantages over conventional means of filling tires from stationarycompressors. Thus there remains a need in the art for an apparatus fullycontained on a vehicle wheel for maintaining desired inflation pressurewithin a tire, without the need for additional components on the frameor body portions of the vehicle, and without the need for replenishmentof batteries or cartridges.

SUMMARY OF THE INVENTION

The present invention comprises a device and method for maintainingdesired inflation pressure within a tire mounted on a rotating wheel ona vehicle, utilizing repeated deformation of the tire where it contactsthe ground. The device includes a small air compressor formed in thewheel in communication with the pressurized tire, responsive todeformation of the tire where it contacts the ground causing compressedair to flow into the tire. As such, desired air pressure in the tire ismaintained directly from the normal rotation of the vehicle wheel bymeans entirely contained on the wheel.

The preferred embodiment includes a small reciprocating piston typecompressor, having a cylinder adapted to receive a sliding pistonresponsive to deformation of the tire, forcing the piston inward on acompression stroke. The compressor is oriented in the wheel such thatrotation of the wheel generates a centrifugal force on the pistonforcing it radially outward on the intake stroke. The preferredembodiment of the invention further includes a plunger in contact withthe inside of the tire and slidably connected to the piston, and aspring disposed between the plunger and the piston. This mechanicalarrangement enables a constant piston displacement responsive to a widerange of deformations of the tire. The compressor of the presentinvention also preferably includes an inlet passageway configured with acentrifugal intake valve, such that the inlet passageway is unsealedonly when the wheel is rotating at a rate sufficient to preventcontaminants from entering therein.

The present invention maintains desired inflation pressure in the tireas follows. The repeated deformation of the rotating tire where itcontacts the ground is transferred to a small air compressor, preferablyof the reciprocating piston type. A plunger is disposed between theinside of the tire and the piston such that the motion of the tiredeformation where the plunger contacts the inside of the tire istransferred to the piston compression stroke, through an intermediaryspring between the plunger and piston. When the point at which theplunger contacts the inside of the tire is not in contact with theground, centrifugal force on the piston and plunger force them radiallyoutward, providing the intake stroke of the compressor. A springcoupling between the plunger and piston provides a constant pistondisplacement responsive to a wide variation in tire deformation. Acentrifugal valve in the inlet passageway to the compressor is normallyclosed by spring pressure, and is opened by centrifugal force when therotational speed of the wheel is great enough so that the centrifugalforce on potential liquid or particulate contaminants expels them awayfrom the inlet passageway, preventing their entry into the compressor.Overcoming normal leakage rates from vehicle tires require extremely lowflow rates from the compressor, requiring extremely low force derivedfrom the deformation of the tire. This invention is analogous to tricklecharging a battery to keep it at full charge.

The device and method of the present invention maintain desiredinflation pressure within a rotating tire, utilizing only repeateddeformation of portions of the tire contacting the ground to operate anair compressor. All components of the device are attached to the vehiclewheel, eliminating the need for any contact with the vehicle body orframe. The invention does not require a gas cartridge or battery mountedto the vehicle wheel, which would need to be periodically replaced orrecharged. Further aspects, objects and advantages will become apparentto those skilled in the art upon reading and understanding of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a vehicle wheel and tire, including across-sectional view of the present invention formed therein.

FIG. 2 is a side view showing the deformed tire and air passing from thecompressor into the tire.

FIG. 3 is a side view showing the wheel rotated 180° and air enteringthe compressor.

FIG. 4 is an enlarged side view of the compressor and the inlet andoutlet passageways.

FIG. 5 is an enlarged front-sectional view of the device of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description and the accompanying drawingsdescribe and illustrate a presently preferred embodiment of theinvention only, and are not intended to limit the scope of the inventionin any way.

The deformation-based tire inflation device 10 of the present inventionis illustrated in FIGS. 1 through 5 which depict a presently preferredembodiment of the invention. Referring first to FIG. 1, the environmentof the present invention is a wheel 12 that supports a tire 14 mountedto said wheel.

Now also referring to FIG. 5, the tire inflation device 10 includes areciprocating piston type air compressor 20 built into the vehicle wheel12, having a piston 22 slidably received within a plunger 40, having abearing pad 44 that contacts the inside surface 15 of the tire 14. Whenthe vehicle wheel 12 is oriented such that the tire 14 contacts theground where the bearing pad 44 contacts the inside of the tire, theplunger 40 causes the piston 22 to slide inward in the compressor 20,constituting a compression stroke (see FIG. 2). When such deformation ofthe tire 14 contacting the bearing pad 44 is not present, centrifugalforces cause the piston 22 to slide outward in the compressor 20,constituting an intake stroke (see FIG. 3).

The tire inflation device 10 also preferably includes a compressionspring 42 captive inside the plunger 40 which the piston 22 bearsagainst. Incorporation of the compression spring 42 and elongate plunger40 allows the tire inflation device 10 to operate for a wide range ofdeformation of the deformed portion 16 of the tire 14 with a limitedpiston displacement, i.e., the device will still operate and not bedamaged by the road surface even when the tire 14 is completely flat. Abalancing weight 15 may be required to maintain the wheel 12 in balance.Though the tire inflation device 10 shown here is formed in the vehiclewheel 12 between the pressurized volume 18 of the tire 14, it iscontemplated that the device 10 could be configured to be physicallylocated within the tire 14 pressurized volume 18 adjacent the wheel 12outboard rim 13, possibly through use of a collapsible plunger 40 toaccommodate maximum deformation.

Now referring to FIG. 4, the air compressor 20 of the preferredembodiment of the present invention may be described. The compressor 20includes an inlet passageway 24 through which air enters the compressor20 cylinder 30. The compressor 20 also includes an outlet passageway 34connected to the pressurized volume 18 of the tire 14. Contained in theinlet passageway 24 and outlet 34 passageway near the cylinder 30 are apair of check valves 25, which provide one-way air flow from the intakeorifice 26 and/or the cylinder 30 into the pressurized volume 18 of thetire 14. The check valves 25 each contain a solid neoprene ball 27 and aporous disc 29 (that allows air to flow through). The check valves 25are arranged such that air is permitted to enter the inlet end andallowed to flow through the outlet end, as the disc 29 prevents the ball27 from seating at the outlet end. The check valves 25 are also arrangedsuch that centrifugal forces do not act upon the balls 27 to bias theirmovement.

The air compressor 20 further includes an adjustment screw 31 (see FIG.5), located in the outside surface (O.S.) of the wheel 12 foraccessibility. The adjustment screw 31 allows the minimum volume of thecylinder 30 of the compressor 20 to be manually varied, effectivelychanging the compression ratio of the compressor 20, thereby determiningthe maximum pressure applied to the pressurized volume 18 of the tire14. Limiting the compression ratio of the compressor 20 limits thepressure generated by the compressor 20, preventing unintentionaloverinflation of the tire 14 and obviating use of a pressure reliefvalve. The adjustment screw 31 may be screwdriver operated to permitmanual adjustments of the maximum pressure of the compressor 20, such anadjustment being calibrated with respect to air pressure at sea level orsome other base altitude. Although the description of the preferredembodiment assumes a compressor 20 comprising a cylinder 30 and a pistonrod 22, the possibility of utilizing other types of compressors iscontemplated, such as a bellows compressor, a diaphragm compressor, alinear compressor, or a rotary compressor.

The inlet passageway 24 preferably includes a centrifugal intake valve50 and filter 52. A centrifugal intake valve 50 is preferably of aspring 53 and plug 51 configuration, the valve 50 being normally closedby the metal strip spring 53 forcing the plug 51 to seal the intakeorifice 26 through which air enters the inlet passageway 24. Thecentrifugal force on the mass of the plug 51 opens the centrifugalintake valve 50 when the vehicle wheel 12 is rotating at a ratesufficient for the centrifugal force on potential liquid and particulatecontaminants to expel such contaminants from the intake orifice 26 andsurrounding area. The centrifugal intake valve 50 permits immersion ofthe wheel 12 in water without allowing water into the inlet passageway24. Because of the especially adverse environment in which vehiclewheels 12 operate, as a further precaution, a conventional air filter 52is included in the inlet passageway 24 between the centrifugal intakevalve 50 and the inlet check valve 25 to reduce the likelihood ofcontaminants entering the compressor 20.

Now referring to FIGS. 2 through 5, the operation and use of thedeformation-based tire inflation device 10 may be more fully described.As the vehicle wheel 12 rotates, initially the portion of the tire 14that the bearing pad 44 contacts is not deformed and a centrifugal forceis placed upon the compressor 20 piston 22 (FIG. 3). As the vehiclewheel 12 rotates, centrifugal force moves the piston 22 radially outwardthereby enlarging the volume in the compressor 20 cylinder 30. Theincreased volume inside the cylinder 30 lowers the pressure to below theoutside air pressure, thereby causing outside air to flow through inletpassageway 24 and into the cylinder 30. An outer stop 38 (FIG. 4) limitsthe outward movement of the piston 22 to control the maximumdisplacement of the intake stroke.

As the vehicle wheel 12 continues to rotate, the tire 14 contacts theground and is deformed at the point at which the bearing pad 44 contactsthe tire 14 (FIG. 2). This causes the plunger 40 to slide inwardradially. This inward motion is transferred to the piston 22 by means ofthe spring 42 until the piston 22 reaches the inner stop 39 (FIG. 4),after which the spring 42 compresses as the plunger 40 follows the fulldeformation of the tire. As the piston 22 and slides inward effectivelyreducing the volume in the compressor 20 cylinder 30, air in thecompressor 20 cylinder 30 is pushed through the outlet passageway 34 andinto the pressurized volume 18 of the tire 14. The compression spring 42or other means disposed between the plunger 40 and the piston 22 makethe tire device 10 operative for a wide range of deformations of thetire 14.

Each intake stroke of the piston rod 22 causes the check valve 25 in theinlet passageway 24 to open, drawing air into the intake orifice 26through the centrifugal intake valve 50, through the filter 52 and intothe compressor 20 cylinder 30. Thereafter, as the piston 22 undertakesthe compression stroke, the check valve 25 in the inlet passageway 24closes, and the check valve 25 in the outlet passageway 34 opens and theair contained within the cylinder 30 is expelled into the pressurizedvolume 18 of the tire 14.

It is understood that the tire inflation system 10 described herein andshown in the drawings represents only a presently preferred embodimentof the invention. Indeed, various modifications and additions includingbut not limited to those discussed above may be made to the preferredembodiment without departing from the spirit and scope of the invention.By way of example only, other means of transferring tire deformation toa compressor may be suitable, such as using the change in width of atire caused by contact of the tire with the ground. These and othermodifications may be obvious to those skilled in the art and may beimplemented to adapt the present invention for use in a variety ofdifferent applications.

What is claimed is:
 1. A device for maintaining desired inflationpressure within a tire mounted on a rotating wheel, said deviceutilizing deformation of said tire as it contacts the ground to pass airinto the tire, the device comprising:an air compressor formed in saidwheel in fluid communication with the tire; the compressor being of thereciprocating piston type, having a cylinder adapted to receive asliding piston; a plunger in contact with the inside of the tire andslidably connected to the piston; and a spring disposed between saidplunger and the piston; deformation of the tire causing said plunger tocompress said spring, said spring then moving said piston inside thecylinder so as to produce a compression stroke.
 2. The device of claim1, wherein:the cylinder has adjusting means to vary the compressionratio, to control the maximum pressure produced by the compressor. 3.The device of claim 1, wherein:the compressor has stopping means, tolimit the movement of the piston.
 4. The device of claim 1, wherein:thecompressor has an inlet passageway through which air is drawn into thecompressor; and said inlet passageway further comprising a centrifugalclosure apparatus, operative to close off the inlet passageway when thewheel is not rotating at a rate sufficient to preclude entry of foreignmatters, but operative to open the inlet passageway when the wheel isrotating at a rate sufficient to expel foreign matters by centrifugalforce.
 5. The device of claim 4, wherein:said centrifugal closureapparatus comprises a spring member having a plug attached thereto, saidplug being positioned relative to the inlet passageway, such that whenthe wheel is rotating at said sufficient rate, the force of said springmember will be overcome by the centrifugal force on said plug to movethe plug away from the inlet passageway, and such that when the wheel isrotating at less than said sufficient rate, the spring member will forcethe plug against the inlet passageway, thereby blocking the inletpassageway.
 6. The device of claim 5, wherein:the inlet passagewayfurther comprises a filter, to preclude contaminants from entering thecompressor.
 7. The device of claim 1, wherein:said plunger is furtherslidable relative the piston at maximum compression, in response tolarge deformation of the tire as a result of very low inflationpressure.
 8. The device of claim 1, wherein:the compressor is formed inthe wheel such that said piston is responsive to centrifugal force fromthe rotation of the wheel to produce an intake stroke in the cylinder.